This invention relates to a grease lubricator particularly for supplying lubricating grease to construction machines, such as hydraulically operated striking tools and crusher jaws. The lubricator includes a grease delivery piston which linearly reciprocates in a work chamber to execute delivery strokes and return strokes, a supply port which opens into the work chamber and which communicates with the lubricating grease container, a delivery port having a closure element yieldingly urged into a closed position and an adjusting abutment which limits the amplitude of the delivery stroke of the delivery piston. The mouth of the supply port merging into the work chamber is, as viewed in the direction of the delivery stroke, situated upstream of the mouth of the delivery port merging into the work chamber and may be at least periodically closed off from the work chamber when the delivery piston moves in the delivery direction beyond the mouth (opening) of the delivery port.
Construction machines, particularly comminuting and crushing apparatus, frequently have guiding and bearing elements which are exposed to high loads and which are lubricated with grease lubricants that expediently have a high or very high solid contents.
U.S. Pat. No. 5,060,761 describes a lubricating device of the above-outlined type, by means of which the chisel of a hydraulic striking tool is automatically lubricated. The device disclosed has a lubricant container whose contents are advanced to a delivery unit by means of a biased compression spring. The delivery unit is provided with a venting valve for eliminating occasionally present air bubbles and has a check valve in the region of its delivery port. By virtue of the check valve only a unidirectional flow is allowed in the delivery port coupled to the work chamber (delivery chamber).
To ensure a satisfactory operation of the delivery unit, any gas (such as air) that has penetrated thereinto when the grease container is replaced, has to be removed by means of the venting valve. Otherwise risks are high that the delivery unit does not convey grease over a substantial period.